Finite Larmor radius effects on the (m = 2, n = 1) cylindrical tearing mode

Abstract

New field solvers are developed in the gyrokinetic code GEM [Chen and Parker, J. Comput. Phys. 220, 839 (2007)] to simulate low-n modes. A novel discretization is developed for the ion polarization term in the gyrokinetic vorticity equation. An eigenmode analysis with finite Larmor radius effects is developed to study the linear resistive tearing mode. The mode growth rate is shown to scale with resistivity as c $ g 1=3 , the same as the semi-collisional regime in previous kinetic treatments Lee, Phys. Fluids 20, 1341 (1977)]. Tearing mode simulations with gyrokinetic ions are verified with the eigenmode calculation. V C 2015 AIP Publishing LLC.

Surface plasmons in superintense laser-solid interactions

“…The issue of understanding the origin of surface ripples was further stimulated by the interest in radiation pressure acceleration [63][64][65][66][67][68] where the rippling instability may cause disruption of the target and affect the spatial quality of the accelerated ions 69 . In the case of thin foil targets, a Rayleigh-Taylor-type instability (RTI) 70,71 has been considered as the most likely mechanism for the rippling onset, but purely hydrodynamic RTI models did not explain the spatial scale of the unstable mode, which was of the order of the laser wavelength λ L as observed in simulations.…”

Verification of long wavelength electromagnetic modes with a gyrokinetic-fluid hybrid model in the XGC code

“…3 in Ref. 32). We did not include an XGC1 data point for η N = 10 −7 because of the very strict resolution requirements of about 2.5 · 10 −4 m or less for this low resistivity.…”

“…For the benchmark against the GEM code, we use the case described in Ref. 32: concentric, circular fluxsurfaces in cylindrical geometry, R 0 = 1.7 m, a = 0.425 m (R 0 /a = 4), B 0 = 1.906 T, q = 1.5[1 + (r/a) 2 ], Z = 1, m i /m p = 2.5, and constant density n 0 = 3.886·10 20 m −3 . Since the electron fluid equations used for this benchmark have no temperature dependence, we can use a constant temperature profile T 0,e = 45.63 eV, which yields the same on-axis β e of 4 · 10 −3 and relative domain size a/ρ i ≈ 740 as in Ref.…”

“…Since the electron fluid equations used for this benchmark have no temperature dependence, we can use a constant temperature profile T 0,e = 45.63 eV, which yields the same on-axis β e of 4 · 10 −3 and relative domain size a/ρ i ≈ 740 as in Ref. 32. The resonant surface for the (2, 1) tearing mode is at (r/a) c ≈ 0.577 corresponding to the normalized poloidal magnetic flux ψ N,c = 0.411.…”

“…The relations between the normalized resistivity η N and growth rate γ N used in Ref. 32 and the corresponding values η e and γ in SIunits are η N = (en 0 /B 0 )η e and γ N = m p /(eB 0 )γ, where m p is the proton mass. The results of a resistivity scan of the growth rate of the (2, 1) tearing mode in this geometry is shown in Fig.…”